Lancets are employed with a variety of devices to make a quick puncture or penetration of the patient's skin in order to obtain a small sample of blood. Various tests may be employed using only small amounts of blood so that the blood flowing from a finger prick is normally sufficient. However, due to the numerous nerve endings in the finger tip area, this procedure may induce a significant amount of pain in the patient even though the skin puncture produces a relatively small cut. Additionally, many patients are required to make numerous finger sticks each day which may result in a coarsening of the finger tip area and a potential loss of tactile discrimination. In order to minimize the potential pain, it is therefore desireable to make the thrust of the lancet through the patient's skin rapidly and at the minimum depth necessary to obtain a sufficient blood sample.
Lancets generally include a body section and a sharpened point extending from one end of the body section. In some instances, the lancet may be physically grasped between the thumb and index finger and made to pierce the skin, for example, the skin of a patient's finger. The lancet is then removed from the puncture and the blood from the puncture site transferred to a blood collection device, such as a capillary tube, micro blood collection tube or diagnostic reagent strip for clinical testing. Numerous problems are associated with such a procedure. For example, the depth of penetration, the force employed in making the puncture, and the angle of insertion and removal vary depending on the person performing the procedure.
More recently, a variety of spring actuated lancet injectors have been designed in an effort to overcome the problems associated with using the lancet alone, however, they have not been entirely satisfactory. For example, some have been relatively complicated in construction and expensive to make. Some constructions require a plurality of springs and a relatively large number of elements for performing such functions as driving, loading and retracting the lancet. Other constructions provide a lancet injector having a fixed, predetermined puncture depth or which are unable to assist in drawing blood from the puncture site. All of the above considerations are particularly important where the puncture is self-made, for example, when a diabetic performs blood glucose testing at home.